Processable polyester compositions

ABSTRACT

A COMPOSITION OF MATTER COMPRISING A POLYESTER OF A BISPHENOL, AT LEAST ONE AROMATIC DICARBOXYLIC ACID, AND AT LEAST ONE AROMATIC HYDROXY ACID, BLENDED WITH FROM ABOUT 2 TO ABOUT 30 PERCENT BY WEIGHT OF A TRIARYL PHOSPHATE, HAVING REDUCED GLASS TRANSITION AND HEAT-DISTORTION TEMPERATURES, THESE COMPOSITIONS BEING MORE AMENABLE TO PROCESSING TECHNIQUES.

United States Patent US. Cl. 26030.6 R Claims ABSTRACT OF THE DISCLOSURE A composition of matter comprising a polyester of a bisphenol, at least one aromatic dicarboxylic acid, and at least one aromatic hydroxy acid, blended with from about 2 to about 30 percent by weight of a triaryl phosphate, having reduced glass transition and heat-distortion temperatures, these compositions being more amenable to processing techniques.

This is a continuation-in-part application of United States Ser. No. 811,667, filed Mar. 28, 1969, now US. Patent 3,576,780.

This invention relates to bisphenol polyester compositions blended with triaryl phosphates, and having markedly improved proces'sability and other desirable properties such as improved flame resistance. More specifically, this invention relates to bisphenol compositions of bisphenols (including aromatic diols and dihydric phenols), aromatic dicarboxylic acids and aromatic hydroxy acids blended with triaryl phosphates.

Bisphenol polyesters of aromatic dicarboxylic acids have high glass transition temperatures and heat-distortion temperatures. Consequently, they also have high melt viscosities and require high processing and fabrication temperatures for forming into shaped articles. The glass transition temperatures, heat-distortion temperatures, melt viscosities, and fabrication temperatures can be reduced by blending various types of compounds with the polyesters. These compounds normally fall into one of two classes, plasticizers or antiplasticizers. Plasticizers increase the elongation and impact strength, but they also decrease the hardness, tensile strength, and stiffness. Antiplasticizers increase the hardness, tensile strength and stiffness but they decrease the elongation and impact strength. The effects of plasticizers and antiplasticizers are discussed in detail in J. Appl. Polymer Sci., 11, 211, 227 (1967). a I

Objects of the present invention, therefore, are: To reduce the glass transition and heat-distortion temperatures, melt viscosities, and fabrication temperatures of bisphenol polyesters without appreciably decreasing the hardness, tensile strength, stiffness, elongation, or impact strength.

Another object of this invention is to provide a commercially practicable methodfor so improving the processability of bisphenol polyesters and to provide such readily processable compositions.

A still further object of this invention is to provide shaped articles of such compositions having a highly useful balance of properties, including exceptional flame resistance.

Other objects will be apparent elsewhere in this specification.

These and other objects hereinafter appearing have been attained in accordance withthe present invention through the discovery that minor amounts of triaryl phosphates in blends with bisphenol polyesters markedly reduce the glass transition and heat-distortion temperatures while maintaining substantially or improving original values of properties such as hardness, tensile strength, stiffness, elongation, impact strength and flame resistance. This discovery is quite unexpected in view of the real adverse effects on impact strength obtained by such additives as triphenyl phosphate and tricresyl phosphate on, for example, bisphenol A polycarbonate as shown in Table 2.

The present invention may be expressed in a broad sense in regard to the composition of matter having markedly reduced melt viscosity, as comprising a bisphenol polyester material, the acid portion of which comprises at least in part an aromatic dicarboxylic acid component, blended with from about 2 to about 30 percent by weight of a triaryl phosphate.

According to one aspect of this invention, there is provided a composition comprising components (1) and (2) as follows:

(1) A polyester of at least one bisphenol, at least one aromatic dicarboxylic acid, or derivatives thereof, and at least one aromatic hydroxy acid, or derivatives thereof, and

(2) From about 2 to about 30 percent by weight, based on the sum of the weights of components (1) and (2), of a triaryl phosphate of the formula wherein R is hydrogen, chlorine, phenyl, or an alkyl radical containing from 1 to 4 carbon atoms.

The aforesaid composition includes polyesters of at least one dihydric phenol, at least one aromatic dicarboxylic acid, and at least one aromatic hydroxy acid, or derivatives thereof.

According to another aspect of this invention there is provided a method for improving the high temper'ature processability of a polyester defined as component (1) above comprising intimately blending-with said component (1) from about 2 to about 30 percent by weight of a triaryl phosphate defined as component (2) above.

In a preferred embodiment of this invention the foregoing objects are accomplished by providing a composition wherein the bisphenol is hydroquinone, the aromatic dicarboxylic acid is isophthalic acid, and the aromatic hydroxy acid is selected from m-hydroxybenzoic acid and p-hydroxybenzoic acid, said polyester being intimately blended with from about 2 to about 30 percent by weight of a triaryl phosphate defined as component (2) above. Preferably from about 5 to about 15 percent by weight of the triaryl phosphate may be used.

The terms an aromatic dicarboxylic acid or derivatives thereof and aromatic hydroxy acid or derivative thereof include, of course, the various condensable derivatives of the acids such as lower alkyl esters or anhydrides which may be employed in such reactions. with diol components of the condensable derivatives to prepare polyesters.

The polyester component of this invention is derived from atleastone bisphenol (including aromatic diols and dihydric phenols). Examples of bisphenols including aromatic diols and dihydric phenols which may be used in this invention include 4,4'-isopropylidenediphenol (also 'known as bisphenol A), 4,4-cyclohexylidenediphenol, 4,4-cyclohexylmethylenediphenol, 4,4 (2 norbornylidene)diphenol, hydroquinone, resorcinol, catechol, 4,4- thiodiphenol, 4,4-sulfonyldiphenol, 4,4-oxydiphenol, 4,4- methylenediphenol, 4,4'-dihydroxybiphenyl, 4,4'-isopropylidenebis(2,6-dichlorophenol), naphthalenediols, and other dihydric phenols listed in US. Pats. 3,03 0,335 and 3,317,- 466. Aliphatic diols (e.g., ethylene glycol or neopentyl glycol) may be used to give copolyesters, but aromatic diols are preferred.

Examples of aromatic dicarboxylic acids which may be used to prepare the polyesters of this invention include terephthalic acid, isophthalic acid, S-tert-butylisophthalic acid, diphenic acid, 4,4-methylenedibenzoic acid, 4,4- oxydibenzoic acid, 4,4-sulfonyldibenzoic acid, naphthalenedicarboxylic acids, chloroterephthalic acid, and dichloroterephthalic acid. The aliphatic (e.g., adipic, azelaic) or alicyclic (e.g., cyclohexanedicarboxylic, norbornanedicarboxylic) acids may be used to give copolyesters, but aromatic dicarboxylic acids are preferred.

Examples of aromatic hydroxy acids which may be used to prepare the polyesters of this invention include o-hydroxybenzoic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, the various naphthalenehydroxycarboxylic acids, and the like. The preferred aromatic hydroxy acid is p-hydroxybenzoic acid. More than one aromatic hydroxy acid may be used.

Most of these bisphenol polyesters and copolyesters can be prepared by ester interchange of the bisphenols with the phenyl esters of the aromatic carboxylic acids. Experimental details are described in various literature and patent references, such as US. Pat. 3,220,977. The polyester may also be prepared from the bisphenols, aromatic hydroxy acid chlorides and dicarboxylic acid chlorides in the presence of tertiary amines, such as described in U.S. Pat. 3,234,168, or by the interfacial polycondensation of bisphenols, aromatic hydroxy acid chlorides and dicarboxylic acid chlorides in an aqueous alkaline medium (US. Pat. 3,216,970). Preferred preparative method consists of heating bisphenol diacetates with aromatic acetoxy carboxylic acids and the aromatic dicarboxylic acids (US. Pat. 3,317,464). Polymers melting above 300 C. are preferably built up in the solid phase fromv prepolymers prepared in the melt.

The triaryl phosphates which are blended with the bisphenol polyesters have the following structure:

wherein R is hydrogen, chlorine, phenyl or an alkyl radical containing from 1 to 4 carbon atoms. Examples include triphenyl phosphate, tricresyl phosphate, tris(o-chlorophenyl) phosphate, tris(p-tert-butylphenyl) phosphate, bis- (p-tert-butylphenyl)phenyl phosphate, Z-biphenylyl diphenyl phosphate, and di(2-biphenyl)phenyl phosphate.

Various conventional techniques may be used to blend the phosphate with the polyester. The two components may be melted together in an inert atmosphere and stirred to effect the blending. The phosphate also may be deposited on the surface of the polyester particles by stirring the particles with a solution of the phosphate in a volatile solvent which will not dissolve or swell the polyester and then evaporating the solvent. Suitable solvents include alcohols, ketones, and saturated hydrocarbons. Better blending is obtained by then melting the coated particles in a screw-fed extruder and extruding the blend. Another blending method is to dissolve the polyester and phosphate together in a volatile solvent, such as chloroform, and then spray-drying.

The blends may contain from about 2 to about 30 weight percent of the triaryl phosphate and preferably from about 5 to 15 weight percent. The higher amounts of phosphate tend to decrease the tensile strength of the polyester but increase the impact strength; they also greatly decrease the heat-distortion temperature and processing temperature as shown in Tables 1 and 2.

Triphenyl phosphate is the preferred phosphate. It is superior to the substituted triaryl phosphates, such as tricresyl phosphate or tri(o-chlorophenyl) phosphate, in that only a nominal decrease in notched Izod impact strength occurs when 10 weight percent is blended with the polyester (Tables 1 and 2). The effects of the preferred triphenyl phosphate on the properties of bisphenol A polycarbonate are shown in Table 2 (Polyester K at top of table). Although the tensile strength is increased, the notched Izod impact strength is very adversely affected (a decrease to 16 percent of the value of the unmodified polymer). The same amount of triphenyl phosphate in Polyester A in the table has almost no effect on the notched Izod impact strength.

Tables 1 and 2 also show that 5-l5 weight percent of the phosphate additives not only does not appreciably decrease the hardness, tensile strength, or stiffness (flexural modulus) of the polyesters but in several cases increases these properties somewhat. Even 30 weight percent of the additives does not appreciably decrease the flexural modulus. These results are very unusual because, as discussed earlier, compounds which are added to lower the fabrication and molding temperatures of poleysters are normally either plasticizers or antiplasticizers. Both of these additives significantly decrease certain properties of the plastic. Plasticizers reduce the hardness, tensile strength, and stiffness whereas antiplasticizers reduce the impact strength. Surprisingly, the triaryl phosphates do not greatly decrease any of these properties.

These additives, in effect, are in the area between plasticizers and antiplasticizers in their effect on plastics. They do not fall under the definition of antiplasticizers in J. Appl. Polymer Sci., 11, 211 (1967) because their glass transition temperature is too low (below -50 C.) and/or their molecular size is too great (over 5.5 A in thickness). As is pointed out in Table VI of this paper (p. 222), the glass transition temperature (T of tri-o-cresyl phosphate is -61 C. The T of triphenyl phosphate is 66 C.

The blends of this invention may also contain various stabilizers, pigments, antioxidants, and other additives. Also, glass or asbestos fibers may be present to improve the stiffness and tensile properties.

The following examples will further illustrate the invention.

BLENDS The blends may be prepared by two exemplary methods. In Method A, the bisphenol polyester is ground to pass a 2-mm. screen and placed in a flask with the triaryl phosphate. The flask is evacuated and released to nitrogen three times to remove all traces of air. It is then heated to 150 C./0.5 mm., and the mixture is slowly stirred for 1 hr. to remove all traces of moisture. The vacuum is released to nitrogen, and the mixture is then stirred under nitrogen at 295340 C. for 30 min. to melt blend the components. After the blend has cooled under nitrogen, it is broken out of the flask and ground to pass a At-inch screen.

In method B, the triaryl phosphate is dissolved in acetone, the polyester (ground to pass a 2-mm. screen) is added, and the phosphate is deposited on the particles as the acetone is evaporated. The particles are dried in an oven at C. and the blend is extruded in a screw-fed extruder (Plasti-Corder from C. W. Brabender Instruments, Inc.,.South Hackensack, N.I.). The extruded rod is cut into pellets.

PHYSICAL PROPERTIES The above blends are injection-molded in a Watson- The' properties of injection'molded plastics in Table 2 are determined with blends prepared by Method B with the following polyesters. For comparative purposes, the polycarbonate of bisphenol A ,(Le'xan 125 from the 5 General Electric Co.) is included at the top of Table 2 and Stillman one-ounce in ection-molding press to g ve -1nch i designated as tensile bars and As-unch fiexure bars. The heat-distortion telmperature of tle 1118x1111? bars at a load of 264 p.s.i. is Polyester Polyester reactants I,V. a so a measure 0 t e g ass transition temperature, which A -Bish lAdi tt 18 decreased by the phosphate additives. Reductlon of the tli ali ndlsogl ilal ic mixture of temp)! glass transition temperature also reduces the melt viscosity; B Bispharwl A (acetate and 80/20 mixture 01 p 7 h t thaiic and isophthalio acids.

18 1s m mated by t e lower molding temperature. The 0 BisphenolAdiacetate and isophthalic acid 0.82 heat-distortion temperatures are measured in a forced- D %,gfgggggfigg fififg gl g gfg f i f Q65 e an en 32% a 6. convection oven (deflection correspondmg to the strain m E flygigqtfiinoniel ei eeta te (65 111.315 pel' ent), 150.

ASTM D648) ASTM procedures are usedfor' measuring 3 6 8 Percent rand 15 benzoic acid (35 mole percent). Rockwell hardness (ASTM D785, Method A), 131 5116 F Hydroquinonediacetate (75 mole pereent),lsophthal- 0.78 strength and elongation (ASTM D1708 flexural modulus g fg g fi gg gggggnt). and p-acetoxybenzolc (ASTM D790), and notched Izod impact strength (ASTM G Bisphenol A diacetate (80 mole percent), terephthal- 0. 70 D256), Method A). The ball-drop impact strength is 30 g g a g gent), and p-acetoxybenzolc determined with 4 x 4 x %-inch plaques (molded in a 6- p TABLE 1' Izod Additive I Tensile, strength, Elongaimpact Molding Heat Rockwell p.s.i. attion at Flexural strength, Conc., mp distortion. hardness, break, modulus, it.-lb./in. Name percent temp., C. L Yield Break percent 10 p.s.i. notch None (control)...--: 0 750 190 107 10, 100 9, 600 47 3.1 2.3 Triphenyl phosphate.. 5 675 160 109 10,700 10,900 58 3.7 2.3 s" as as 13% as a n 15 .0 Tricresyl hosphate .1 10 625 128 114 10,800 10,100 36 3.6 1. 1 Tris (o-ch orophenyl) hosphate- 10 675 150 113 10,500 9,700 36 3.0 0.8 Bis (p.tertbutylpheny phenyl phosphate 10 650 140 1 114 10,500 10,000 40 3.5 1.6 2-biphenylyl diphen'yl phosphate... 10 675 137 119 10, 700 10, 600 62 3. 7 1. 7 Dn 600 as 105 8,800 9,700 70 as 1.0 Do so 550 so 80 6,700 6,400 84 3.0 as

1 The ball-drop impact strength is 23 it.-lb. as compared to 14 it.-1b. for the control containing no additive.

ounce. injection-molding machine). The inherent viscosities (I.V.) are determined at C. in 60/40 phenol/ tetrachloroethane at a concentration of 0.23 g./ 100 ml.

The properties of injection-molded plastics in Table 1, above, are determined with blends made by Method A with a polyester (I.V. 0.80) prepared from bisphenol A diacetate and equimolar amounts of terephthalican'd isophthalic acids.

It is also surprising that the phosphate additives are so stable at the extremely high temperatures required for in- 40 jection-molding the polymers and that they do not contribute to polymer instability. Tables 1 and 2 show the use of the additives at molding temperatures of 675-725 P. (357-385" C.). Similar additives have been used to plasticize other classes of polymers, but thetemperatures involved were considerably lower.

TABLE 2 t Izod Additive Tensile Elongaimpact Molding Heat Rockwell strength,p.s.l.attion at Flexurai strength, Conc., tempi distortion hardness, break, modulus, it.-lb./ln. Polyester Name percent temp., C. L. Yield Break percent 10 l p.s.i. notch K 0 650 148 94 9, 000 9, 800 67 3. 1 9.1 K 10 600 103 93 10, 200 13, 000 102 3. 2 1. 4 A 0 750 194 110 10,500 9, 500 19 3. 1 2. 7 A 2 725 190 111 10, 500 12. 400 3. 2 3. 2 A 10 675 135 108 10, 400 9, 000 16 3. 5 2. 6 A 20 575 83 96 8, 000 9, 200 80 3. 2' 2. 8 A 30 550 54 58 5, 800 6,200 98 2.8 6.8 p 10 650 130 112 10, 700 .000 15 3. 5 1. 3 B; None (control) 0 750 197 107 10,200 10,500 32 3.1 4.4 B Di(2-biphenyl) phenyl phos- 16 650 114 106 200 10,300 3. 3 4,0

' e. C N ne (control) 0 700 179 107 10, 200 10, 600 2.9 4.2 O- Trlphonyl phosphate 10 650 122 107 10, 400 10, 62 3. 2 3. 8 D. None (contro 0 775 225 106 10,000 9, 800 50 2.9 1.5 D Triphenyl phospha 15 625 114 101 9, 800 10,000 44 t 3.0 1.4 D Trlcresyl phosphate. 15 625 r 104 10,200 10,300 38 3.2 0.9 E None (control) 0 750 178 104 10,700 11,000 63 3. 2 7. 4 E Triphenyl hosphate 10 625 126 103 10,000 11, 000 88 3.3 4. 2 E Tricresyl p osphate 10 625 121 106 10,800 10,100 42 3. 6 3. 2 E Tris(o-chlorophenyl) hosphate. 10 675 136 106 10, 600 9, 900 38 3. 3 2. 5 E- Di(l2-l%ipheny1)pheny phos- 10 675 108 10,900 10. 600 34 3.7 3.0 p a e.

F None (control) 0 O) F Triphenyl phosphate. 10 I 700 128 101 None 13, 400 22 4. 1 0. 3 F do 15 #675 107 96 None 14, 000 ,36 I 4. 2 0.4 F rin 25 I 650 81 82 9.400 9,200 55 3.6 1.2 G None (control) 0 750 195 104 None 10,500 38 3. 1 2.4 G Triphenykphosphate- 5 700 165 105 9,900 10,300 40 3.2 2.0 G Tricresyl phosphate 10 650 107 10,600 10,400 28 3.4 0.8

1 Cannot be molded at maximum temperature capability of injection-molding machine, 775 F. (412 C.) because 01 high crystalline polymer melting point (370 0.).

I Molded specimens crystallized on cooling to give increased strength and stiffness and decreased impact strength.

It is also very surprising that these phosphate additives have a very significant effect in reducing the flammability of the plastics even though only a small amount of phosphorus is present in the final product. It is known that the presence of phosphorus reduces the flammability, but it is surprising to find that the presence of only 0.95 percent phosphorus has a considerable elfect: percent triphenyl phosphate in polyester A of Table 2 increases the oxygen index by the Oxygen Index Flammability Test from 0.37 to 0.46. This test is described in Modern Plastics, November 1966, p. 141. The above index values indicate that 37 percent oxygen in an oxygen/nitrogen mixture will sustain candle-like burning of a molded bar containing no phosphate whereas 46 percent oxygen is required to sustain combustioon when 10 weight percent triphenyl phosphate is also present (0.95 percent phosphorus in the bar). Triaryl phosphates which also contain halogen, e.g., tris(o-chlorophenyl) phosphate impart even greater fire-retardant properties.

Tables 1 and 2 above illustrate the results which are obtained when the polymers are molded on a small, oneounce, ram-type, injection-molding press. Higher impact strengths can sometimes be obtained with large reciprocating screw injection-molding machines. The following properties are obtained with 0.125-inch thick bars molded on a Van Dorn 200RS-6, 6-ounce machine, using Va-inch pellets of polyester A (I.V. 0.69) and Az-inch pellets of the same polymer (I.V. 0.69) containing 10 percent triphenyl phosphate (TPP):

The bisphenol polyester/triaryl phosphate blends of this invention also may be used as melt adhesive bonding agents. Polyester A above has a tensile shear strength on 0.064-inch cold-rolled steel of 2300 p.s.i. whereas the same polyester blended with 10 weight percentof triphenyl phosphate (properties in Table 2) has a tensile shear strength of 2800 p.s.i. on the steel. The bonds are prepared by placing a film of the polyester between the steel substrates, clamping together, and immersing in a Woods metal bath for 3 minutes. Because of the presence of the additive, the adhesive bonds are prepared at 320 C. (340 C. required for the control containing no additive). This blend also has good tensile shear strength on aluminum, titanium, chrome-plated steel, and glass. Other blends in Tables 1 and 2 also have good adhesion to these substrates.

Although this invention has been described in detail with particular reference to preferred embodiments thereof, it will be understood that variations and modifications can be eifected within the spirit and scope of the invention.

I claim:

1. Composition comprising components (1) and (2) as follows:

( 1) a polyester derived from at least one bisphenol,

or ester forming derivatives thereof, at least one aromatic dicarboxylic acid, or ester forming derivatives thereof, and at least one aromatic hydroxy acid, or ester forming derivatives thereof, and

(2) from about 2 to about 30 percent by weight, based on the sum of the weights of components (1) and 2) of a triaryl phosphate of the formula wherein R is hydrogen, chlorine, phenyl, or an alkyl radical containing from 1 to 4 carbon atoms. 2. The composition of claim 1 wherein the bisphenol is bisphenol A.

3. Composition comprising components (1) and (2) as follows:

(1) a polyester derived from at least one dihydric phenol, or ester forming derivatives thereof, at least one aromatic dicarboxylic acid, or ester forming derivatives thereof, and at least one aromatic hydroxy acid, or ester forming derivatives thereof, and

(2) from about 2 to about 30 percent by weight, based on the sum of the weights of components (1) and (2), of a triaryl phosphate of the formula wherein R is hydrogen, chlorine, phenyl, or an alkyl radical containing from 1 to 4 carbon atoms.

4. The method for improving the high temperature processability of a bisphenol polyester defined as component (1) of claim 1 comprising intimately blending with said component (1) from about 2 to about 30 percent by weight of triaryl phosphate defined as component (2) I of claim 3.

5. A shaped article of a composition as defined by claim 3.

6. The composition of claim 3 wherein the dihydric phenol is hydroquinone.

7. The composition of claim 3 wherein the acid portion of the polyester comprises from 1 to mole percent of either terephthalic acid, isophthalic acid, or mixtures thereof.

8. The composition of claim 3 wherein the triaryl phosphate is triphenyl phosphate.

9. The composition of claim 3 wherein the dihydric phenol is hydroquinone, the acid portion of the polyester is isophthalic acid and the aromatic hydroxy acid portion of the polyester is p-hydroxybenzoic acid, or m-hydroxybenzoic acid, or mixtures thereof.

10. The composition of claim 3 wherein the dihydric phenol is resorcinol.

References Cited UNITED STATES PATENTS 3,576,780 4/1971 Jackson 260--30.6 R 3,428,714 9/1969 Sconco 260-306 R LEWIS T. I ACOBS, Primary Examiner Pgggn UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIQN patengN Dated November 21, 1972 h Winston J. Jackson, Jr.

' It is'cerrified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 65, delete "di(2biphenyl)phenyl"' and insert -di(2 b iphenylyl)phenyl-.

Column 4, line I 22, delete "16" andins'erh -l5--. Column 4, line 34,- delete "'p oleysters" and insert polyesters-.

Column 7, line 15,. delete combustioon'T and insert eombustion.-

Signed and sealed this 1st, day 5r May 1973.

(SEAL) Attest:

'QDZJARD M. FLETCHER, (TR, 1 ROBERT GOTTSCHALK Attesting; Offi eeI I v Commissioner of Patents 

